DE102017102344A1 - Printed circuit board for an electric motor, method for producing a printed circuit board for an electric motor and electric motor - Google Patents

Abstract

The invention relates to a printed circuit board for an electric motor, comprising a coil formed from at least one conductor track running spirally within a layer of the printed circuit board, and a coil core made of a ferromagnetic or ferrimagnetic material extending in a direction perpendicular to the printed circuit board Position is arranged, wherein the coil core is disposed completely within the circuit board and electrically insulated from the environment of the circuit board. Furthermore, the invention relates to a method for producing a printed circuit board for an electric motor, comprising the following method steps: - generating a coil which is formed from at least one spirally extending within a layer of the circuit board trace, - generating a coil core of a ferromagnetic material, the extending in a direction which is perpendicular to the layer, - arranging the coil core completely within the circuit board, - generating an electrical insulation of the coil core relative to the environment of the circuit board.

Description

The invention relates to a printed circuit board for an electric motor, with a coil which is formed from at least one spirally extending within a layer of the printed circuit board conductor track. Furthermore, the invention relates to an electric motor with such a printed circuit board and a method for producing such a printed circuit board.

Such printed circuit boards can be used in electric motors which have one or more coils integrated in a printed circuit board. Such electric motors are also referred to as printed circuit board motors or printed circuit board (PCB) motors and can be designed as a rotary motor or as a linear motor.

A circuit board for an electric motor of the aforementioned type is for example from the DE 10 2008 062 575 A1 known. This circuit board has a spirally extending conductor track, which is provided within a layer of the printed circuit board and thus forms an ironless, compact and weight-saving coil. In order to dissipate the heat generated during operation, a cooling surface is arranged within the spiral-shaped conductor track, which is electrically isolated from the spirally extending conductor track.

Electric motors with such printed circuit boards have proven themselves in practice. However, it has turned out to be disadvantageous that the force which can be provided by such electric motors is limited.

Based on such a prior art, it is an object of the invention to provide a printed circuit board for an electric motor, which is suitable for applications with high power requirements.

To solve the problem, a printed circuit board for an electric motor is proposed, with a coil which is formed from at least one helically extending within a layer of the circuit board trace, and with a coil core of a ferromagnetic or ferrimagnetic material which extends in a direction which is arranged perpendicular to the layer, wherein the coil core is disposed completely within the circuit board and electrically insulated from the environment of the circuit board.

By the coil core of a ferromagnetic or ferrimagnetic material of the magnetic flux generated by the coil can be bundled and thereby the magnetic flux density can be increased. When using the circuit board in an electric motor, increasing the magnetic flux density causes the magnetic force to increase. The electric motor can provide a higher force or torque. The arrangement of the bobbin completely within the circuit board allows a compact design of the electric motor. Since the coil core, whose material can be electrically conductive, is electrically insulated from the environment, the electrical insulation of the coil core relative to the coil can be smaller than would be the case with a coil core which is not electrically insulated from the environment. The conductor track of the coil can thereby be arranged close to the coil core, whereby the efficiency of the coil and thus also of the electric motor increases.

The bobbin may be formed of a ferromagnetic material having iron, cobalt or nickel. The material of the spool core may be a ferromagnetic alloy or a ferrite. The bobbin may have sheets and / or pressed powder material. The coil core preferably has a soft magnetic compound (SMC) material.

According to a preferred embodiment of the invention, the circuit board has a plurality of coils, which are formed from at least one spirally extending within a layer of the circuit board trace, and a plurality of cores of a ferromagnetic or ferrimagnetic material extending in a direction perpendicular to the position is arranged, wherein the coil cores are arranged completely within the circuit board and electrically insulated from the environment of the circuit board. The coils formed in the printed circuit board can be excited independently of each other during operation of the electric motor. The coil cores are arranged separately from each other within the circuit board, whereby magnetically separated teeth of an electric motor can be formed.

A structurally advantageous embodiment provides that the coil is designed such that in the interior of the coil, a magnetic field can be generated, which is aligned perpendicular to a plane of the circuit board.

According to a preferred embodiment, it is provided that the circuit board has a first dielectric layer, in particular a first dielectric cover layer, and / or a second dielectric layer, in particular a second dielectric cover layer, over which the coil core is insulated from the surroundings of the circuit board. The first and / or the second dielectric layer can prevent unwanted touching of the coil core in the sense of basic insulation and offer protection against electric shock. The coil core preferably extends in a direction perpendicular to the first dielectric layer and / or or the second dielectric layer is arranged. The first and / or second dielectric layer are thus preferably arranged parallel to the at least one layer in which the coil is formed.

In this context, it has been found to be particularly preferred if the circuit board has an insulating region for insulating the coil core relative to the coil of a dielectric material which is arranged between the coil core and the conductor track of the coil, wherein the first dielectric layer and / or the second dielectric layer has a larger breakdown voltage and / or a greater insulation resistance than the insulating region. In such a configuration, it is possible to provide a base insulation with a higher breakdown voltage and / or a higher insulation resistance via the first dielectric layer and the second dielectric layer, and a functional insulation with a lower breakdown voltage and / or a lower insulation resistance via the insulating region between the coil core and the coil.

Particularly advantageous is an embodiment in which the insulating region and the first dielectric layer and the second dielectric layer are formed of the same dielectric material and a first thickness of the insulating region is less than a second thickness of the first dielectric layer and less than a third Thickness of the second dielectric layer. This makes it possible to arrange coil and coil core closer together and thereby increase the efficiency of the coil and the electric motor. Alternatively, the insulating region may be formed of a different dielectric material than the first dielectric layer and the second dielectric layer, wherein the first thickness of the insulating region is greater than the second thickness of the first dielectric layer and greater than the third thickness of the second dielectric Layer.

According to a preferred embodiment, the first dielectric layer and / or the second dielectric layer is formed of an FR4 material, preferably of an FR4 material having a thermal conductivity of at least 0.5 W / (mK), more preferably of an FR4 material with a thermal conductivity of at least 1 W / (mK). During operation of the coil, heat is generated due to the ohmic resistance of the conductor track. Among other things, the heat has to be removed from the printed circuit board via the first and / or second dielectric layer. FR4 material with a thermal conductivity of at least 0.5 W / (mK), in particular of at least 1 W / (mK), has proved to be particularly suitable for assisting the dissipation of heat and preventing unwanted temperature-induced failure of the coil.

An embodiment has proven to be advantageous in which the printed circuit board comprises a recess which penetrates the first dielectric layer and / or the second dielectric layer. Through the recess, the conductor track of the coil can be electrically contacted without affecting the electrical insulation of the coil core relative to the environment. For contacting the coil, an electrically conductive material can be introduced into the recess. Alternatively, it is possible to arrange a connector in the recess. The recess may be formed as Tiefenfräsung or deep hole.

The printed circuit board preferably has at least one thermo-via of electrically conductive material which extends in a direction which is perpendicular to the electrically conductive layers and which is electrically insulated from the coil and / or the coil core. More preferably, the thermal via extends from the first dielectric layer through the interior of the circuit board to the second dielectric layer, so that the dissipation of heat from the interior of the circuit board is improved. The transfer of heat from the thermal via to the environment may then be through the first and / or second dielectric layers.

According to a preferred embodiment, the circuit board on a first part of the circuit board and a second part of printed circuit board, which are interconnected, in particular glued, are. For this purpose, an outer layer of the first partial printed circuit board can be connected to an outer layer of the second partial printed circuit board. The first partial printed circuit board preferably has the first dielectric cover layer on an opposite side to the second partial printed circuit board, and the second partial printed circuit board has the second dielectric cover layer on an opposite side from the first partial printed circuit board.

The object mentioned in the introduction is also achieved by an electric motor, in particular a rotary motor or a linear motor, which has a printed circuit board as described above.

• - Erzeugen einer Spule, die aus mindestens einer spiralförmig innerhalb einer Lage der Leiterplatte verlaufenden Leiterbahn gebildet ist,
• - Erzeugen eines Spulenkerns aus einem ferromagnetischen Material, der sich in einer Richtung erstreckt, die senkrecht zu der Lage angeordnet ist,
• - Anordnen des Spulenkerns vollständig innerhalb der Leiterplatte,
• - Erzeugen einer elektrischen Isolation des Spulenkerns gegenüber der Umgebung der Leiterplatte.

To achieve the object, a method for producing a printed circuit board for an electric motor is further proposed, which comprises the following method steps:

• Generating a coil which is formed from at least one conductor track extending spirally within a layer of the printed circuit board,
• - Generating a coil core of a ferromagnetic material, which in a Extends direction, which is arranged perpendicular to the position,
• Arranging the spool core completely within the printed circuit board,
• - Generating electrical insulation of the coil core relative to the environment of the circuit board.

In the electric motor and the method for producing a printed circuit board, the same advantages can be achieved as have already been described in connection with the printed circuit board.

The production of the printed circuit board preferably takes place in such a way that first of all a total printed circuit board, which is also referred to as a utility, is produced, which comprises a plurality of printed circuit boards. The production of this total printed circuit board preferably comprises the abovementioned process steps for producing a printed circuit board. In a subsequent method step, the overall printed circuit board can then be singulated into individual printed circuit boards, for example by a separating device, in particular a milling device, a cutting device or a punching device.

According to a preferred embodiment of the method, the electrical insulation of the coil core relative to the environment of the circuit board comprises a cover layer which completely covers a surface of the circuit board, wherein a recess, in particular a deep milling or deep hole, is produced by the cover layer. In a subsequent method step, a contacting of the conductor track of the coil can then take place through the recess, for example, by introducing into the recess an electrically conductive material or a plug connector.

In this context, it has been found to be advantageous if the electrical insulation of the coil core relative to the surroundings of the printed circuit board comprises a cover layer which completely covers a surface of the overall printed circuit board, wherein a recess, in particular a deep milling or deep hole, is produced by the cover layer. In a subsequent method step, the separation of the total printed circuit board to individual printed circuit boards can take place.

• 1 eine Leiterplatte gemäß einem ersten Ausführungsbeispiel der Erfindung in einer horizontalen Schnittdarstellung entlang einer zur Plattenebene der Leiterplatte parallelen Schnittebene;
• 2 eine Leiterplatte gemäß einem zweiten Ausführungsbeispiel der Erfindung in einer schematischen, vertikalen Schnittdarstellung entlang einer zur Plattenebene der Leiterplatte senkrecht orientierten Schnittebene; und
• 3 eine Leiterplatte gemäß einem dritten Ausführungsbeispiel der Erfindung in einer vertikalen Schnittdarstellung entlang einer zur Plattenebene der Leiterplatte senkrecht orientierten Schnittebene; und
• 4 eine Leiterplatte gemäß einem vierten Ausführungsbeispiel der Erfindung in einer vertikalen Schnittdarstellung entlang einer zur Plattenebene der Leiterplatte senkrecht orientierten Schnittebene.

Further details and advantages of the invention will be explained below with reference to the embodiments illustrated in the figures. Hereby shows:

• 1 a circuit board according to a first embodiment of the invention in a horizontal sectional view along a plane parallel to the plane of the circuit board cutting plane;
• 2 a circuit board according to a second embodiment of the invention in a schematic, vertical sectional view along a plane perpendicular to the plane of the circuit board oriented cutting plane; and
• 3 a circuit board according to a third embodiment of the invention in a vertical sectional view along a plane perpendicular to the plane of the board printed cutting plane; and
• 4 a circuit board according to a fourth embodiment of the invention in a vertical sectional view along a plane perpendicular to the plate plane of the circuit board cutting plane.

In the 1 is a sectional view through a circuit board 1 shown according to a first embodiment of the invention. The cutting plane is parallel to the board plane of the circuit board 1 through an inner layer of the printed circuit board 1 , The inner layer of the circuit board 1 has several tracks 3 on, which are spirally formed, so that within this position a plurality of coils 2 are formed. By means of each coil 2 a magnetic field can be generated which is perpendicular to the plane of the board 1 - here the cutting plane - is aligned. The magnetic field has its maximum in the middle of the respective through the conductor track 3 formed spiral.

The conductor track 3 is formed of a metallic material, preferably of a copper-containing material, more preferably of copper. The conductor track 3 is of a dielectric material 5 surrounding the individual sections of the spiral track 3 electrically isolated from each other. In the dielectric material 5 it is preferably an FR4 material.

In addition to that in the 1 shown position of the circuit board 1 indicates the circuit board 1 more layers on. In this respect, it is the circuit board 1 a multi-layer board, which is also referred to as a multi-layer board. The circuit board 1 can have four, eight, ten, twelve, fourteen or more layers, wherein in each layer tracks are arranged. The interconnects of the other layers preferably also have a spiral-shaped structure, so that coils are also formed in these layers. The tracks of each adjacent layers are connected to each other via so-called vias, electrically conductive connections perpendicular to the plane of the plate. At the in 1 shown location are, for example, vias 6 provided, which the conductor tracks 3 connect to the tracks of the adjacent layers so that coils 2 are formed, which extend in a direction perpendicular to the plane of the plate.

The circuit board 1 also has several thermal vias 7 on that the dissipation of heat from inside the circuit board 1 improve and are described in more detail below in connection with FIG. 3. For mounting the circuit board 1 inside an electric motor are also recesses 8th provided in the form of through holes.

Inside the circuit board 1 are also several separate coil cores 4 made of a ferromagnetic or ferrimagnetic material. Every spool core 4 extends in a direction perpendicular to the layers of the circuit board 1 is arranged. The coil core 4 is formed of sheets and / or layers of pressed powder material. In the material of the spool core 4 it is iron, a ferromagnetic alloy or a ferrite. The coil core 4 is each within the spiral track 3 provided, which is a coil 2 forms. Through the coil core 4 will be the one from the coil 2 generated magnetic flux bundled and strengthens the magnetic flux density.

The coil cores 4 are completely inside the circuit board 1 provided and opposite the environment of the circuit board 1 electrically isolated. The insulation of the coil cores 4 occurs via a first dielectric layer, which is parallel to the layers of the circuit board 1 is arranged, for example, a dielectric cover layer, the circuit board 1 , Over the first dielectric layer, the respective coil core 4 on a first surface of the circuit board 1 be isolated from the environment. Furthermore, the circuit board 1 a second dielectric layer also parallel to the layers of the circuit board 1 is arranged. The coil cores 4 are inside the circuit board 1 disposed between the first and second dielectric layers. In this respect, each coil core 4 to the environment through the first dielectric layer on a first surface of the circuit board 1 isolated and through the second dielectric layer on a second surface opposite to the first surface.

The first and second dielectric layers are formed of FR4 material. The thermal conductivity of the FR4 material is preferably at least 0.5 W / (mK), more preferably at least 1 W / (mK), so that the resulting during operation of the coil ohmic heat dissipation improved by the first and second dielectric layer led outwards can.

The first and second dielectric layers provide a base insulation of the spool core 4 ready for the environment of the circuit board. The arrangement of the coil cores 4 completely within the circuit board 1 not only allows a compact design of the electric motor, but also allows the provided inside the circuit board insulation between the respective bobbin 4 and the associated coil 2 weaker and thus the performance of the coil 2 or the electric motor, in which the circuit board 1 is used to boost. These advantages will be explained in more detail below with reference to the illustration in FIG. 2.

The 2 shows a second embodiment of a circuit board according to the invention 1 for an electric motor. Unlike the in 1 shown embodiment is in 2 just a coil core 4 shown. The circuit board 1 of the second embodiment, as well as the circuit board after 1 , several separate coil cores 4 of a ferromagnetic or ferrimagnetic material. On a first surface of the circuit board 1 , hereinafter referred to as the top, is a first dielectric layer 9 intended. At a second surface of the printed circuit board opposite the first surface 1 , hereinafter referred to as the bottom, is a second dielectric layer 10 arranged. The coil core 4 is thus inside the circuit board 1 between the first dielectric layer 9 and the second dielectric layer 10 arranged. The first dielectric layer 9 forms a cover layer at the top of the circuit board 1 and the second dielectric layer 10 forms a cover layer on the underside of the circuit board 1 ,

The representation in 2 further shows a position of the circuit board 1 , a spiral track 3 having. In addition to the position shown can be more layers with spiral trace 3 be present, which with the conductor track 3 the position shown are electrically connected. For electrical insulation of the conductor track 3 opposite the spool core 4 is an insulating area 11 the situation provided. The insulating area 11 is formed of a dielectric material, for example of an FR4 material. The material of the insulating area 11 and / or the dimensioning of the insulating region 11 is selected such that the first dielectric layer 9 and the second dielectric layer 10 have a larger breakdown voltage and / or a greater insulation resistance compared to the insulating region. Thus, via the first dielectric layer 9 and the second dielectric layer 10 the basic insulation of coil and coil core are made possible with respect to the environment. The insulation between the conductor track 3 the coil 2 and the bobbin only needs to meet the lower requirements of functional insulation. Optionally, it may be provided that the insulating region 11 and the first dielectric layer 9 and the second dielectric layer 10 are formed of the same dielectric material and a first thickness D1 of the insulating area 11 less than a second thickness D2 the first dielectric layer 9 and less than a third thickness D3 the second dielectric layer 10 , Alternatively, it is possible for the insulating area 11 is formed of a different dielectric material than the first dielectric layer 9 and the second dielectric layer 10 , where the first thickness D1 of the insulating area 11 is greater than the second thickness D2 the first dielectric layer 9 and larger than the third thickness D3 the second dielectric layer 10 , For example, the first thickness D1 of the insulating region in the range of 200 .mu.m to 300 .mu.m, and the second thickness D2 the first dielectric layer 9 and the third thickness D3 the second dielectric layer 10 may be in the range from 110 μm to 190 μm, preferably in the range from 140 μm to 160 μm, particularly preferably at 150 μm.

The 3 shows a detail of a circuit board 1 according to a third embodiment of the invention in a sectional view along a plane of the board to the board 1 vertically oriented cutting plane. The circuit board 1 has a plurality of layers, wherein in the layers a plurality of coils, not shown, are provided, which are formed from at least one spirally extending within a layer of the printed circuit board trace. Further, the circuit board has a plurality of coil cores made of a ferromagnetic or ferrimagnetic material, which extend in a direction which is perpendicular to the electrically conductive layers, wherein the coil cores completely within the circuit board 1 arranged and opposite the environment of the circuit board 1 are electrically isolated. To insulate the coil core from the environment are at the circuit board 1 a first dielectric layer 9 and a second dielectric layer 10 intended.

To dissipate heat from inside the circuit board 1 are also thermal vias 7 provided, one of which in the 3 is recognizable. The thermo-via 7 is made of electrically conductive material extending in a direction which is perpendicular to the electrically conductive layers and which is electrically insulated from the coil and / or the coil core.

The production of in 1 . 2 and 3 shown circuit board 1 can be done with a method in which initially a coil 2 is generated, which consists of at least one spiral within a layer of the circuit board 1 running conductor track 3 is formed. Optionally, the coil can 2 over several layers of the circuit board 1 extend, wherein the tracks of adjacent layers are interconnected via vias. In a further method step, a receptacle for the spool core is inserted into the printed circuit board 4 brought in. The introduction of the recording can be done for example by milling. The receptacle extends perpendicular to the position with the coil 2 and is within the spiral path of the track 3 arranged the respective coil.

Further, a spool core 4 generated, which is dimensioned such that it can be fully absorbed in the recording. This may for example be formed as a package of a plurality of sheets or as a molded body of a pressed powder material, in particular as a shaped body, which is formed of a plurality of layers of pressed powder material. The coil core 4 is finally introduced into the receptacle in the circuit board.

Finally, an electrical insulation of the coil core relative to the environment of the circuit board is generated. It is preferred when generating the insulation, for example in the form of the first dielectric layer 9 and / or the second dielectric layer 10 , the recording closed to the environment.

In the 4 is a fourth embodiment of a guide plate according to the invention 1 shown. This circuit board 1 has a first part circuit board 12 and a second part circuit board 13 on, which are interconnected, in particular glued, are. For the production of the printed circuit board 1 becomes an outer layer 14 the first part PCB 12 with an outer layer 15 the second part circuit board 13 connected, for example glued. At the side of the first part PCB 12 that the interconnected outer layers 14 . 15 the part circuit boards 12 , 13 is opposite, has the first part circuit board 12 a first dielectric capping layer 9 on. At the side of the second part PCB 13 that the interconnected outer layers 14 . 15 the part circuit boards 12 . 13 opposite, has the second part circuit board 13 a second dielectric capping layer 10 on.

The circuit board 1 has a spiral shape within a layer of the printed circuit board 1 running tracks 3 which form a coil. There is also a coil core 4 made of a ferromagnetic or ferrimagnetic material which is perpendicular to the layers or to the dielectric cover layers 9 . 10 is arranged. The coil core 4 lies within the through the first part PCB 12 and the second part circuit board 13 formed circuit board 1 and is through the first and second dielectric capping layers 9 . 10 isolated from the environment.

The printed circuit boards described above 1 for an electric motor each have a coil 2 on the at least one spiral within a layer of the circuit board 1 running conductor track 3 is formed, and a bobbin 4 out a ferromagnetic or ferrimagnetic material extending in a direction perpendicular to the layer, the coil core 4 completely within the circuit board 1 arranged and opposite the environment of the circuit board 1 is electrically isolated. The printed circuit boards described 1 can be used in an electric motor, in particular a rotary motor or a linear motor.

LIST OF REFERENCE NUMBERS

1

circuit board

2

Kitchen sink

3

conductor path

4

Plunger

5

dielectric material

6

Via

7

Thermo-Via

8th

recess

9

first dielectric layer

10

second dielectric layer

11

insulating area

12

Supply PCB

13

Supply PCB

14

backsheet

15

backsheet

D1

Thickness of the insulating area

D2

Thickness of the first dielectric layer

D3

Thickness of the second dielectric layer

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008062575 A1 [0003]

Claims (11)

Printed circuit board for an electric motor, comprising a coil (2) which is formed from at least one conductor track (3) extending spirally within a layer of the printed circuit board (1), characterized by a coil core (4) made of a ferromagnetic or ferrimagnetic material which is located in a direction which is arranged perpendicular to the layer, wherein the coil core (4) is arranged completely inside the printed circuit board (1) and is electrically insulated from the surroundings of the printed circuit board (1). PCB after Claim 1 , characterized in that it comprises a plurality of coils (2) formed from at least one conductor track (3) extending spirally within a layer of the printed circuit board (1), and a plurality of coil cores (4) made of a ferromagnetic or ferrimagnetic material which are in extend a direction which is arranged perpendicular to the layer, wherein the coil cores (4) are arranged completely inside the printed circuit board (1) and electrically insulated from the environment of the printed circuit board (1). Printed circuit board according to one of the preceding claims, characterized in that the coil (2) is formed such that in the interior of the coil (2), a magnetic field can be generated which is aligned perpendicular to a plane of the printed circuit board (1). Printed circuit board according to one of the preceding claims, characterized in that the printed circuit board (1) has a first dielectric layer (9), in particular a first dielectric cover layer, and / or a second dielectric layer (10), in particular a second dielectric cover layer which of the coil core (4) is insulated from the surroundings of the printed circuit board (1). PCB after Claim 4 , characterized in that the circuit board (1) has an insulating region (11) for insulating the coil core (4) from the coil (2) made of a dielectric material between the coil core (4) and the conductor track (3) of the coil (2), wherein the first dielectric layer (9) and / or the second dielectric layer (10) compared to the insulating region (11) has a greater breakdown voltage and / or a greater insulation resistance. PCB after one of the Claims 4 to 5 characterized in that the first dielectric layer (9) and / or the second dielectric layer (10) is formed from an FR4 material, preferably from an FR4 material having a thermal conductivity of at least 0.5 W / (mK), particularly preferably from an FR4 material with a thermal conductivity of at least 1 W / (mK). PCB after one of the Claims 4 to 6 characterized by a recess, in particular a deep groove or deep hole, which penetrates the first dielectric layer (9) and / or the second dielectric layer (10). Printed circuit board according to one of the preceding claims, characterized by at least one thermal via (7) made of electrically conductive material which extends in a direction which is perpendicular to the electrically conductive layers and which is opposite to the coil (2) and / or the Coil core (4) is electrically insulated. Electric motor, in particular a rotary motor or linear motor, characterized by a circuit board (1) according to one of the preceding claims. Method for producing a printed circuit board (1) for an electric motor, comprising the following method steps: Generating a coil (2) which is formed from at least one conductor track (3) extending spirally within a layer of the printed circuit board (1), Producing a coil core (4) of a ferromagnetic material which extends in a direction which is perpendicular to the layer, Arranging the spool core (4) completely within the printed circuit board (1), - Generating an electrical insulation of the coil core (4) relative to the environment of the circuit board (1). Method according to Claim 10 , characterized in that the electrical insulation of the coil core (4) relative to the environment of the printed circuit board (1) comprises a cover layer which completely covers a surface of the printed circuit board (1), wherein a recess, in particular a Tiefenfräsung or deep hole, produced by the cover layer becomes.

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